The Cochrane Collaboration has mainly focussed on evidence-based medicine through systematic reviews (SR) and meta-analysis (MA) of clinical trials. Preclinical (animal) studies focus on mechanism-based research for medical purposes and establishing safety and efficacy of medical treatments for human patients. SRs and MA of animal studies are not yet the routine, even though there are very good reasons for doing so. For example, serious side effects occurring during trials in patients could have been predicted when a MA of animal studies had been performed (Horn et al. 2001, Pound et al. 2004). Within medicine, animal studies are used to predict efficacy and safety of new treatments, and establish possible mechanisms of human disease. Surprisingly, animal studies are not analysed to the full extent before clinical trials are performed, even though there are very good reasons for doing so: see e.g. (1) Drug side effects: Horn et al., 2001; Pound et al. 2004; (2) Evidence-based choice of animal model: de Vries et al. 2012, Van Drongelen et al. 2012; (3) Translational value: Hooijmans et al. 2012; Sena et al. 2010, Macleod et al. 2012. By establishing synergy between SRs of animal and clinical studies, a significant contribution to translational medicine comes within reach. By performing SRs of animal studies, (1) transparency is created towards a more evidence-based choice of animal models in relation to clinical problems, (2) higher scientific quality of animal studies (more reliable results) will be induced and (3) a better basis for the design of clinical trials is created. Target audience and level of expertise: Anybody interested in the design and conduct of SRs in animal studies.